This invention relates to an enclosure, and particularly though not exclusively to one for use with a cable, for example a cable joint or termination.
The enclosure of the invention finds particular application to electric, and especially power, cables, but is also applicable to other cables, for example telecommunications cables.
For convenience only and not by way of limitation, the invention will be discussed with reference to an electric power cable joint. When two power cables are to be jointed, the outer layers thereof are successfully stripped back to expose the conductors. The electrical connection between the conductors is then effected in any convenient manner. The outer layers of the cables then need to be replaced by fresh components in order to restore electrical and mechanical integrity, and this may be effected in various ways, using various technologies, including tape wrapping. Heat shrink technology, for example using heat recoverable polymeric sleeves and kits from Tyco Electronics Raychem GmbH, has been known and used successfully for many years, often in preference to the traditional filling of a casing with hot bitumen or epoxy resin.
As an alternative to heat-shrinkable sleeves, elastic sleeves that are recoverable around a cable joint without the application of heat thereto have been available for some time. One example of such a sleeve is that sold by 3M under the tradename PST, which consists of an elastomeric cylindrical sleeve that is held out in an expanded configuration by a rigid inner spiral member. These sleeves, mounted on their hold-outs, are positioned over the cable joint, and the hold-out is then removed from inside the sleeve. Other elastic sleeves are known which are held out in an expanded configuration on a rigid support member with an end of the sleeve folded back on top of the portion of the sleeve which is in direct contact with the tubular support, as described by 3M in EP-A-0767523. When the tubular hold-out is positioned over the cable joint, the folded-back portion of the sleeve may be rolled over the end of the hold-out to form a bridge that contracts elastically down onto the cable. It is observed in EP-A-0767523 that the removal of the spiral holdouts is problematic and that physical stress relief adaptations are necessary for the folded-back sleeves.
WO-A-9113756 describes a revolvable double-wall elastomeric sleeve, available from Tyco Electronics Raychem GmbH under the tradename RAYVOLVE, that has a lubricant enclosed by the double wall of the sleeve. This sleeve, which is not previously expanded, can be rolled onto a cable to one side of the jointing area, which usually involves having to increase the sleeve diameter by up to a factor of two or more, and subsequently can be revolved back across the formed joint. The lubricant facilitates the revolving of the two, inner and outer, walls of the sleeve over one another. The lubricant remains within the sealed double wall of the sleeve, allowing the sleeve to be revolved away and re-used, if the joint needs to be reentered. A RAYVOLVE sleeve is usually employed to provide at least some of the insulation over the cable joint, and may, for example, functionally replace the outer jacket of the cable at the cable joint.
It is an object of the present invention to provide an improved enclosure for a substrate. In accordance with one aspect of the present invention, there is provided an enclosure for mounting on a substrate, comprising a rigid tubular support member and a revolvable elastic sleeve having a double wall enclosing lubricant sealed therein, wherein the sleeve is mounted on the support member in an expanded state with a portion of the inner wall of the sleeve secured to the support member so that the sleeve can be revolved over the end of the support member to contract elastically to a less expanded state while retaining a portion of the sleeve on the support.
Thus, the revolvable sleeve is retained attached to the support member but is able to be revolved off the member so as to be recovered to a smaller size around the underlying substrate, in conformity therewith. The retention of the sleeve at one end on the support member allows the positioning of the other end of the sleeve on the substrate after deployment to be controlled, thus ensuring, for a given enclosure and substrate, not only that sufficient overlap onto the substrate is achieved, but also that the sleeve does not roll too far off the support member. The revolvable nature of the sleeve inherently facilitates re-entry of the substrate, for example a cable joint, if required. The provision of the support member provides for storage of the sleeve prior to initial installation and also during any re-entry of the substrate. It has been found that the support member may be economically manufactured, for example by simply cutting and de-burring suitable lengths from an extruded plastics tube, advantageously omitting any special stress relief adaptations. This advantage may possibly result from the self-reinforcing effect of the double-wall sleeve, which resists damage at the end regions of the support member more effectively that single-wall folded-back sleeves.
The sleeve may be secured to the support member by any suitable means. It is envisaged that this may be by bonding, for example using an interposed adhesive, and/or by mechanical compression around the outside of the sleeve, for example using a hose clamp or roll spring, and/or by being compressed onto the inner surface of the support member by an inner expandable means. The sleeve may thus conveniently be sealed to the support member. Typically, the support member is of substantially elongate cylindrical shape, with the sleeve being secured to or adjacent one end thereof.
A further sleeve, similar to the aforementioned sleeve, may be mounted on and secured to the support member, typically providing an arrangement whereby the sleeves can be revolved down off respective ends of the support member onto the substrate, for example a cable each side of a joint, whilst remaining secured on to the support member by the said portions. The or each sleeve is preferably a RAYVOLVE sleeve. Such sleeves are disclosed in European Patent Application Publication Nos. 0 209 399, 0 210 061, 0 210807 and 0 212 851, the entire disclosures of which are incorporated herein by this reference,
A sealant such as a mastic, may be provided, advantageously on the substrate or on the sleeve, to seal the sleeve or sleeves to the substrate.
The rigid support member can thus provide mechanical protection for the substrate. Advantageously, it is made from a plastics material. The support member may also provide an electrical function, especially when the enclosure surrounds an electric cable. For example, it may provide an electrically insulating layer. The support member may be made of metal, or otherwise be metallic, for example being metallised, and thus may provide electrical continuity or earthing over the substrate, or electrical screening thereof.
Storing the double-walled lubricated elastic sleeve in an expanded configuration, on the rigid support member, avoids the need to urge it into an expanded condition as it is revolved up onto a substrate, such as a cable joint. Unlike known single layer expanded elastic sleeves, the lubricant stays in place, it does not dry out, and it is not exuded from the interface between the sleeve and the support member, so that removal of the sleeve from the tubular hold-out member is facilitated. The sleeve may be expanded to between, say, two and four times its original diameter, thus providing an enclosure, having a suitably sized rigid support member, with a good range-taking capability. The sleeve can thus be revolved off the support member onto the substrate with the application of little force, even though its rubber wall has been stored in a stretched configuration for some time, with the enclosed lubricant having been subjected to high pressure. The enclosure has a comparatively small overall length, since the sleeve (or sleeves) can be stored thereon within its overall length.